[media] mb86a20s: fix demod settings

With the current settings, only one channel locks properly.
That's likely because, when this driver was written, Brazil
were still using experimental transmissions.

Change it to reproduce the settings used by the newer drivers.
That makes it lock on other channels.

Tested with both PixelView SBTVD Hybrid (cx231xx-based) and
C3Tech Digital Duo HDTV/SDTV (em28xx-based) devices.

Cc: stable@vger.kernel.org
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>